This invention is related to microemulsions that contain cosmetically active ingredients. In a preferred embodiment, this invention is related to antiperspirant salt-containing microemulsions that are stable, clear liquids and are easy and inexpensive to produce.
The microemulsions of the present invention contain water. Microemulsions of the present invention are transparent or translucent, optically isotropic and thermodynamically stable mixtures of oil and water stabilized by surfactants and perhaps co-surfactants. The particle size of the dispersed phase of a microemulsion is about 100 to about 2000 angstroms, more preferably are about 100 to about 1000 angstroms. They can form spontaneously or with a little energy. Therefore they are simple to prepare and are not process dependent i.e. the order of addition of starting materials or speed/type of mixing is not critical to the preparation of the microemulsions. It would be desirable to formulate antiperspirant compositions using microemulsions because microemulsions are easy and inexpensive to process and can be inherently clear without requiring refractive index matching of the aqueous and non-aqueous phases.
Microemulsions have attracted considerable technological and scientific interest. Water-in-oil (w/o) microemulsions containing water, an ionic surfactant, a cosurfactant and oil are the most investigated. The ionic surfactantxe2x80x94containing microemulsions usually exhibit stability over a large range of temperature. When inorganic salts are added, the minimum surfactant level to form water-in-oil microemulsions will increase. As the hydrocarbon oil chain length increases, the solubilization of aqueous phase into the oil phase decreases, while the liquid crystal area increases. Nonionic surfactant-containing water-in-oil microemulsions require a large amount of surfactant as well. Unfortunately, nonionic surfactant-containing microemulsions commonly exhibit a small temperature range of stability
Microemulsions exist in the following forms: as water-in-oil, oil-in-water or as a bicontinuous phase, which is also called the surfactant phase. As used herein, the term xe2x80x9cmicroemulsion means water-in-oil, oil-in-water or a bicontinuous phase, or mixtures thereof. Bicontinuous phase microemulsions are found to solubilize a high amount of water and oil with lower levels of surfactant. The region around a bicontinuous phase microemulsion may transition into a swollen lamellar phase, otherwise known as a liquid crystal phase, and in certain cases these phases (microemulsion and liquid crystal) may co-exist. These phases exhibit birefringence, shear induced (streaming) birefringence, and are thixotropic, viscoelastic and transparent. Because some of these systems exhibit increased viscosity the technical literature may refer to them as microemulsion gels.
It is an object of the present invention to provide antiperspirant compositions, which contain high levels of antiperspirant salts, cosmetic oils and surfactants suitable for application to the axilla. It is also an object of the present invention to provide antiperspirant compositions that do not require refractive index matching of the aqueous and nonaqueous phases in order to be clear. It is also an object of the present invention to provide microemulsion antipersprirant compositions that require little energy to manufacture. These and other objects of the present invention will become more readily apparent in the present application.
Patents and patent documents, which are cited in connection with the disclosed invention, are as follows:
DE 196 42 090 A1 discloses cosmetic or dermatologic compositions based on microemulsions.
U.S. Pat. No. 5,162,378 discloses water in oil microemulsions comprising cetyl dimethicone copolyol, water, silicone, alcohol, and 5-40% by weight of one or more salts.
U.S. Pat. No. 5,705,562 discloses a method of spontaneously forming a highly stable clear microemulsion by combining water, a volatile cyclic methyl siloxane or a volatile linear methyl siloxane and a silicone polyether surfactant. U.S. Pat. No. 5,707,613 is in the same patent family as the just mentioned patent.
WO 94/22420 is concerned with silicone-based skin care products, which are applied to the skin as aerosols and form a clear gel on the skin.
WO 94/19000 discloses pharmaceutical compositions in the form of a microemulsion which comprise and oil, a mixture of high and low HLB surfactants in which the high HLB surfactant comprises an aliphatic, aryl or aliphatic-aryl sulfate or sulfosuccinate or salt thereof, an aqueous phase and a biologically active agent.
WO 94/08610 discloses pharmaceutical compositions in the form of microemulsions which comprise an oil, a mixture of high and low HLB surfactants in which the high HLB surfactant comprises a medium-chain fatty acid salt, an aqueous phase and a biologically active agent.
U.S. Pat. No. 5,575,990 discloses roll-on antiperspirant compositions which are clear and, when applied to the human skin, do not leave a visible white residue after drying. The clear antiperspirant roll-on compositions are stable under varying temperature conditions and provide a suitable cosmetically acceptable feel or sensation when applied to the human skin.
U.S. Pat. No. 5,487,887 discloses roll-on antiperspirant compositions and more particularly concerns antiperspirant compositions which are clear and stable under varying temperature conditions and, when applied to the human skin, do not leave a visible white residue after drying. The compositions in the form of an oil-in-water microemulsion, comprise an antiperspirant active 5-30, PEG-7-glyceryl cocoate 5-25, emollients 0.5-3, cyclomethicone 3-7, and water 53-60%.
The invention relates to a composition in the form of a microemulsion comprising an antiperspirant salt, a cosmetic oil, and a combination of at least one cationic quaternary surfactant and at least one nonionic surfactant.